Selectivity of Hydrophilic and Hydrophobic TiO₂ for Organic‐Based Dispersants

Abstract

The effects of the surface chemistry of TiO2 powders on the dispersion performance of various dispersants are studied. Four common dispersants (oleic acid, oleylamine, oleyl phosphate, and tris‐(2‐butoxyethyl) phosphate) with different functional groups (carboxyl (–COOH), amino (–NH2), phosphate (–P(=O)(OH)2), and –P(=O)) are investigated for their potential to disperse hydrophilic and hydrophobic titania (TiO2) powders. The outcomes, based on adsorption kinetics, adsorption isotherms, rheologies, and theoretical calculations, indicate that the hydrophilic TiO2 is more sensitive to the chemistry of dispersants as compared to the hydrophobic TiO2. However, the relative dispersion efficiencies of the dispersants are not found relevant to the adsorption kinetics, which is dominated by the adsorption amount. In addition, hydrogen bonding between –OH groups of the phosphate‐based dispersants dominates their dispersion ability for TiO2.

New Approach for the Synthesis of Nanozirconia Fortified Microcapsules

“…43,44 Notably, an α of 1 indicates a suspension with well-dispersed Newtonian flow containing no agglomerates. Upon the addition of 2 wt % OP, the apparent (1) excessive OP led to specific interactions such as hydrogen bonding and polymer bridging between particles, 45,46 causing nanopowder agglomerates to form and increasing the apparent viscosity; and (2) the intrinsic viscosity of the added OP enhanced the overall apparent viscosity.…”

“…V t was calculated as the sum of the attractive (V A ) and repulsive (V R ) energies. The minimum potential energy required for the stabilization of particles is generally 15 kT; 43,46,47 thus, in theory, the ZrO 2 nanopowder can be dispersed and stabilized if the adsorption thickness (δ) of OP is larger than 1.2 nm. According to the saturated adsorbance of OP (A s ; Figure S1), the projected radius (⟨S 2 ⟩ 1/2 ) of adsorbed OP on ZrO 2 was determined to be 0.5 nm by eq 1.…”

“…This plot clearly shows that viscosity was minimized at [OP] = 2 wt % and inversely to increase at [OP] > 2 wt %, although α remained at approximately 0.90–0.92 for [OP] from 2 to 40 wt %. There are two possible explanations for the inversely increased apparent viscosity: (1) excessive OP led to specific interactions such as hydrogen bonding and polymer bridging between particles, , causing nanopowder agglomerates to form and increasing the apparent viscosity; and (2) the intrinsic viscosity of the added OP enhanced the overall apparent viscosity.…”

“… where M is the molecular weight of OP, S A is the specific surface area of powder, and N is Avogadro’s number. This indicates that OP was probably adsorbed vertically on the particle surface, and the thickness of the adsorption layer should be approximately the molecular length of OP (∼2 nm). , Thus, OP was theoretically available for the stabilization and dispersion of ZrO 2 nanopowder.…”

Interaction of Polyphenylsilsesquioxane With Various β-diketonate Complexes of Titanium By Mechanochemical Activation

“…Titanesiloxanes can also be obtained by mixing titanium dioxide nanoparticles with a ready-made polymer matrix, as it was done by the authors of works [30][31][32][33], by sol-gel synthesis based on titanium alkoxides [34][35][36]. The processes of direct interaction of titanium alkoxides with hydromethylsiloxane, as well as cleavage of the siloxane bond in the copolymer hydromethylsiloxane-phenylmethylsiloxane under the action of tetrabutoxytitanium, have been studied [37].…”